Base station apparatus and communication control method

ABSTRACT

A base station apparatus for communicating to a mobile station over a downlink shared channel includes a reception unit configured to receive downlink radio quality information from the mobile station over a control channel frequency-multiplexed with an uplink shared channel, a measurement unit configured to measure a radio quality of the control channel, and a determination unit configured to determine reliability of the downlink radio quality information based on the radio quality. Also, a communication control method at a base station apparatus for communicating to a mobile station over a downlink shared channel includes receiving downlink radio quality information from the mobile station over a control channel frequency-multiplexed with an uplink shared channel, measuring a radio quality of the control channel, and determining based on the radio quality whether the mobile station has transmitted the downlink radio quality information.

TECHNICAL FIELD

The present invention relates to base station apparatuses andcommunication control methods to which OFDM (Orthogonal FrequencyDivision Multiplexing) is applied in downlinks.

BACKGROUND ART

A communication scheme serving as a successor of W-CDMA and HSDPA, thatis, a LTE (Long Term Evolution) system has been and is being discussedby a W-CDMA standardization organization 3GPP. In the LTE system, anOFDM scheme and a SC-FDMA (Single-Carrier Frequency Division MultipleAccess) scheme are being investigated as downlink and uplink radioaccess schemes, respectively. See 3GPP TR 25.814 (V7.0.0), “PhysicalLayer Aspects for Evolved UTRA”, June 2006, for example.

In the OFDM scheme, a frequency band is segmented into multiple smallerfrequency bands (subcarriers), and data is carried and transmitted overthe individual subcarriers. According to the OFDM scheme, thesubcarriers are densely arranged on the frequency band in such a mannerthat the subcarriers are partially overlapped with each other withoutmutual interference, resulting in fast transmission and highly efficientutilization of the frequency band.

In the SC-FDMA scheme, a frequency band is segmented, and differentfrequency bands are used among multiple terminals for transmission,resulting in reduced interference among the terminals. According to theSC-FDMA scheme, variations in transmit power are reduced, resulting inlower power consumption for the terminals and wider coverage.

The above-mentioned LTE system uses shared channels in uplinks anddownlinks. For example, in uplink, a base station apparatus selectsmobile stations to communicate to the base station apparatus using theshared channel for each subframe (each 1 ms) and uses downlink controlchannels to instruct the selected mobile stations to communicate overthe shared channel in certain subframes. The mobile stations transmitthe shared channels in accordance with the downlink control channels.The base station apparatus receives and decodes the shared channelstransmitted from the mobile stations. The above-mentioned selection ofmobile stations to communicate over the shared channels is called asscheduling.

Also, AMC (Adaptive Modulation and Coding) is applied to the LTE system,and thus different transmission formats for the shared channels are usedfor different subframes. The transmission formats may include assignmentinformation of resource blocks, which corresponds to frequencyresources, modulation schemes, payload sizes, HARQ related informationsuch as redundancy version parameters and process numbers, and/or MIMOrelated information such as reference signal sequences for MIMOapplication, for example.

In the LTE, identification information of the mobile stationscommunicating over the shared channels in the subframes and thetransmission formats of the shared channels are transmitted overphysical downlink control channels (PDCCHs). The PDCCH may be alsoreferred to as DL L1/L2 control channels.

In a MAC layer of the LTE, HARQ (Hybrid Automatic Repeat reQeust) isapplied in both uplinks and downlinks. For example, the mobile stationstransmit acknowledgement information in uplinks based on CRC checkresults of DL-SCH. The base station apparatus controls retransmissionsdepending on the acknowledgement information. The acknowledgementinformation is represented as either of a positive response (ACK)indicating that transmitted signals have been successfully received or anegative response (NACK) indicating that the transmitted signals havenot been successfully received. Also, the base station apparatustransmits acknowledgement information in downlinks based on CRC checkresults of UL-SCH. The mobile station controls retransmission dependingon the acknowledgement information. The acknowledgement information isrepresented as either of a positive response (ACK) indicating thattransmitted signals have been successfully received or a negativeresponse (NACK) indicating that the transmitted signals have not beensuccessfully received.

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

In the above-mentioned scheduling and HARQ operations, if PDCCHs fortransmitting the identification information of mobile stationscommunicating over uplink shared channels and transmission formats forthe shared channels are erroneously decoded at a mobile station, themobile station may not transmit the uplink shared channels. On the otherhand, the base station apparatus reserves the uplink shared channels forthat mobile station, resulting in inefficient utilization of resources.

Also, if PDCCHs for transmitting the identification information ofmobile stations communicating over downlink shared channels andtransmission formats for the shared channels are erroneously decoded ata mobile station, the mobile station fails to receive the downlinkshared channels and accordingly does not transmit acknowledgementinformation for those downlink shared channels. In this case, the basestation apparatus has to determine whether the mobile station hasactually transmitted the acknowledgement information. Theacknowledgement information does not include an error check functionsuch as CRC. Thus, if the determination is not made at the base stationapparatus, the acknowledgement information would be determined to beeither ACK or NACK, and particularly the determination that theacknowledgement information is ACK may be problematic.

Thus, the present invention addresses the above-mentioned problem, andone object of the present invention is to provide a base stationapparatus and a communication control method that can perform schedulingand HARQ operations properly in uplinks and downlinks of LTE systems.

Means for Solving the Problem

In order to the above-mentioned problem, one aspect of the presentinvention relates to a base station apparatus for communicating to amobile station over a downlink shared channel, including: a receptionunit configured to receive downlink radio quality information from themobile station over a control channel frequency-multiplexed with anuplink shared channel; a measurement unit configured to measure a radioquality of the control channel; and a determination unit configured todetermine reliability of the downlink radio quality information based onthe radio quality.

A further one aspect of the present invention relates to a communicationcontrol method at a base station apparatus for communicating to a mobilestation over a downlink shared channel, the method including: receivingdownlink radio quality information from the mobile station over acontrol channel frequency-multiplexed with an uplink shared channel;measuring a radio quality of the control channel; and determining basedon the radio quality whether the mobile station has transmitted thedownlink radio quality information.

ADVANTAGE OF THE INVENTION

According to the embodiments of the present invention, it is possible toprovide a base station apparatus and a communication control method thatcan perform scheduling and HARQ operations properly in uplinks anddownlinks of LTE systems.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a radio communication systemaccording to one embodiment of the present invention;

FIG. 2 is a schematic diagram illustrating a relationship between PUCCHsand PUSCHs according to one embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating an arrangement of a slot anda subframe according to one embodiment of the present invention;

FIG. 4 is a partial block diagram illustrating a base station apparatusaccording to one embodiment of the present invention;

FIG. 5 is a first schematic diagram illustrating a temporal relationshipbetween operations at a base station apparatus and a mobile stationaccording to one embodiment of the present invention;

FIG. 6 is a second schematic diagram illustrating a temporalrelationship between operations at the base station apparatus and themobile station according to one embodiment of the present invention;

FIG. 7 is a third schematic diagram illustrating a temporal relationshipbetween operations at the base station apparatus and the mobile stationaccording to one embodiment of the present invention;

FIG. 8A is a partial block diagram illustrating a baseband signalprocessing unit in the base station apparatus according to oneembodiment of the present invention;

FIG. 8B is a partial block diagram illustrating the layer 1 processingunit in the base station apparatus according to one embodiment of thepresent invention;

FIG. 8C is a partial block diagram illustrating the layer 1 processingunit in the base station apparatus according to one embodiment of thepresent invention;

FIG. 8D is a partial block diagram illustrating the layer 1 processingunit in the base station apparatus according to one embodiment of thepresent invention;

FIG. 9 is a flowchart illustrating a transmission determination methodaccording to one embodiment of the present invention;

FIG. 10 is a flowchart illustrating an acknowledgement determinationmethod according to one embodiment of the present invention;

FIG. 11 is a flowchart illustrating a CQI reliability determinationmethod according to one embodiment of the present invention;

FIG. 12 is a flowchart illustrating an acknowledgement informationreception method according to one embodiment of the present invention;

FIG. 13 illustrates exemplary segmentation of resources in PUCCH; and

FIG. 14 is a flowchart illustrating a CQI reception method according toone embodiment of the present invention.

LIST OF REFERENCE SYMBOLS

-   200: base station apparatus-   202: transmit and receive antenna-   204: amplification unit-   206: transmitting and receiving unit-   208: baseband signal processing unit-   210: call processing unit-   212: channel interface-   2081: layer 1 processing unit-   2082: MAC processing unit-   2083: RLC processing unit

BEST MODE FOR CARRYING OUT THE INVENTION

Best modes for carrying out the present invention are described below inconjunction with embodiments with reference to the accompanyingdrawings.

Throughout all the drawings for illustrating the embodiments, elementsand components having the same function are referred to as the samereference numerals and are not repeatedly described.

[Description of Radio Communication System and Communication Channels]

A radio communication system where a base station apparatus according toone embodiment of the present invention is used is described withreference to FIG. 1.

A radio communication system 1000 may be an Evolved UTRA and UTRAN (alsoreferred to as Long Term Evolution or Super 3G) applied system andincludes a base station apparatus eNB (eNode B) 200 and multiple mobilestation apparatuses or user equipment (UE) 100 _(n) (100 ₁, 100 ₂, 100₃, . . . , 100 _(n) where n is a positive integer). The base stationapparatus 200 is connected to an upper station such as an access gatewayapparatus 300, which is connected to a core network 400. In thisembodiment, the mobile station apparatuses 100 _(n) communicate to thebase station apparatus 200 within a cell 50 in accordance with theEvolved UTRA and UTRAN.

Hereinafter, unless specifically stated otherwise, it is assumed thatthe mobile stations 100 _(n) have the same arrangement, function andstate.

In the radio communication system 1000, the OFDM and the SC-FDMA areused as radio access schemes in downlinks and uplinks, respectively. Asmentioned above, the OFDM is a scheme where a frequency band issegmented into smaller frequency bands (subcarriers) and data istransferred over the individual subcarriers. The SC-FDMA is a schemewhere a frequency band is segmented and segmented different frequencybands are used among multiple terminals for transmission, resulting inreduction in interference among the terminals.

Communication channels in the Evolved UTRA and UTRAN are describedbelow.

For downlinks, a PDSCH (Physical Downlink Shared Channel) shared amongthe mobile station apparatuses 100 _(n) and a PDCCH (Physical DownlinkControl Channel) for LTE are used. In the downlinks, the LTE PDCCH isused to transmit information on users which PDSCH is transmitted to andtransport formats of the PDSCH, information on users which transmitsPUSCH (Physical Uplink Shared Channel) and transport formats,acknowledgement information for the PUSCH or others. Also, user data istransmitted in PDSCH. The user data is transmitted in a DL-SCH(Downlink-Share Channel) as a transport channel.

The above-mentioned information on users which PDSCH is transmitted andtransport formats of the PDSCH may be referred to as downlink schedulinginformation, downlink scheduling grant or downlink assignmentinformation. Also, the above-mentioned information on users whichtransmits PUSCH and transport formats of the PUSCH may be referred to asuplink scheduling grant.

For uplinks, the PUSCH (Physical Uplink Shared Channel) shared among themobile station apparatuses 100 _(n) and a LTE control channel are used.As illustrated in FIG. 2, the control channel includes two types ofchannels, a channel time-multiplexed with the PUSCH and a channelfrequency-multiplexed with the PUSCH. The frequency-multiplexed channelis referred to as a PUCCH (Physical Uplink Control Channel). Thetime-multiplexed channel may be mapped into the top of a subframe asillustrated in FIG. 2 or into any other position within the subframe.For example, the time-multiplexed channel may be mapped into a SC-FDMAsymbol near a SC-FDMA symbol into which a demodulation reference signalis mapped.

In the uplinks, the LTE PUCCH is used to transmit downlink qualityinformation (CQI: Channel Quality Indicator) used for scheduling of thePDSCH and AMC (Adaptive Modulation and Coding) and acknowledgementinformation for the PDSCH (HARQ ACK information). Also, the PUSCH isused to transmit user data. The user data is transmitted in a UL-SCH(Uplink-Shared Channel) as a transport channel.

For uplink transmissions, seven SC-FDMA symbols are used per slot. Asingle subframe consists of two slots. Thus, the single subframeconsists of 14 SC-FDMA symbols as illustrated in FIG. 3. A demodulationreference signal (demodulation RS) for data demodulation is mapped intotwo of the 14 SC-FDMA symbols. Also, a sounding reference signal(sounding RS) used to determine a transmission format for the PUSCH,such as scheduling, uplink AMC and TPC, is transmitted in one of the 14SC-FDMA symbols other than the two SC-FDMA symbols assigned for thedemodulation RS. However, the sounding RS does not have to be mappedinto all subframes. In the SC-FDMA symbols for transmitting the soundingRS, sounding RSs from multiple mobile stations are multiplexed inaccordance with CDM (Code Division Multiplexing). For example, thedemodulation RSs may be mapped into the fourth and eleventh SC-FDMAsymbols within one subframe. Also, the sounding RS may be mapped intothe first SC-FDMA symbol within one subframe, for example.

Note that in addition to the above-mentioned CDM, block spreadmultiplexing may be applied.

As illustrated in FIG. 3, a data modulation reference signal togetherwith data is transmitted in uplink transmissions. Thus, it can bedetermined whether a data transmission is occurring by only checking thedemodulation reference signal.

[Arrangement of Base Station Apparatus]

The base station apparatus 200 according to one embodiment of thepresent invention is described with reference to FIG. 4.

In this embodiment, the base station apparatus 200 includes a transmitand receive antenna 202, an amplification unit 204, a transmitting andreceiving unit 206, a baseband signal processing unit 208, a callprocessing unit 210 and a channel interface 212.

User data transmitted from the base station apparatus 200 to the mobilestation 100 _(n) in downlinks is supplied to the baseband signalprocessing unit 208 from an upper station of the base station apparatus200, such as the access gateway apparatus 300, via the channel interface212.

The baseband signal processing unit 208 performs transmission operationsin a PDCP layer, transmission operations in a RLC layer such assegmentation and concatenation of the user data and RLC (Radio LinkControl) retransmission control, MAC (Medium Access Control)retransmission control such as HARQ (Hybrid Automatic Repeat reQuest)transmission operations, scheduling, transmission format selection,and/or channel decoding, IFFT (Inverse Fast Fourier Transform) andforwards the resulting data to the transmitting and receiving unit 206.Also, The baseband signal processing unit 208 performs transmissionoperations such as channel coding and IFFT on signals in the PDCCHserving as a downlink control channel and forwards the resulting signalto the transmitting and receiving unit 206.

The transmitting and receiving unit 206 performs frequency conversionfor converting base band signals supplied from the baseband signalprocessing unit 208 into a radio frequency band, which is subsequentlyamplified at the amplification unit 204 and transmitted via the transmitand receive antenna 202.

On the other hand, for data transmitted from the mobile station 100 _(n)to the base station apparatus 200 in uplinks, a radio frequency signalreceived at the transmit and receive antenna 202 is amplified at theamplification unit 204 and frequency-converted into a baseband signal atthe transmitting and receiving unit 206. Then, the baseband signal issupplied to the baseband signal processing unit 208.

The baseband signal processing unit 208 performs a FFT operation, anIDFT operation, error correction decoding, a reception operation for MACretransmission control, a reception operation at the RLC layer and/or areception operation at the PDCP layer on user data in the suppliedbaseband signal and supplies the resulting signal to the access gatewayapparatus 300 via the channel interface 212.

As will be described with reference to FIG. 5, the baseband signalprocessing unit 208 evaluates power of the uplink shared channel anddetermines whether the mobile station has actually transmitted theuplink shared channel. Uplink resource management is performed based onthe determination.

FIG. 5 illustrates the above-mentioned operations of the mobile station100 _(n) and the base station apparatus 220 from the temporal viewpoint.As illustrated in FIG. 5A, for example, at step 1002, the base stationapparatus 200 informs the mobile station 100 _(n) in subframe #i of anID for a user communicating over the PUSCH in subframe #i+3 and/ortransport format information for the user data, that is, the uplinkscheduling grant. At step 1004, the mobile station 100 _(n) receives aPDCCH in subframe #i. At step 1006, if the ID for the user communicatingover the PUSCH in subframe #i+3 within the PDCCH matches the ID of themobile station 100 _(n), the mobile station 100 _(n) transmits a PUSCHin subframe #i+3 based on the transport format information in the PDCCH,that is, the uplink scheduling grant. At step 1008, the base stationapparatus 200 receives the PUSCH in the subframe #i+3 from the mobilestation which the base station apparatus 200 informs that the mobilestation should communicate over the PUSCH at timing 1002.

As illustrated in FIG. 5B, if the mobile station 100 _(n) fails toreceive the PDCCH (1012) from the base station apparatus 200successfully at step 1014, the mobile station 100 _(n) does not transmitthe PUSCH in subframe #i+3 at step 1016. As a result, at step 1018, thebase station apparatus 200 would fail to receive the PUSCH in subframe#i+3 from the mobile station 100 _(n). Thus, the base station apparatus200 could make power determination for the uplink shared channel bychecking the data demodulation reference signal at steps 1008 and 1018.

In the above-mentioned example, the power determination is made for thePUSCH corresponding to the uplink scheduling grant, which is the ID forthe user communicating over the PUSCH and/or the transport formatinformation for the user data. The uplink scheduling grant istransmitted to the mobile station 100 _(n) in subframe #i. In otherembodiments, the same power determination can be applied to a PUSCH(UL-SCH) retransmitted in response to a NACK being transmitted asacknowledgement information to the PUSCH (UL-SCH). Exemplary operationsof the mobile station 100 _(n) and the base station apparatus 200 inthis case are described with reference to FIG. 6.

As illustrated FIG. 6A, for example, the base station apparatus 200informs the mobile station 100 _(n) in a PDCCH in subframe #i of an IDfor a user communicating over a PUSCH in subframe #i+3 and/or transportformat information for the user data, that is, uplink scheduling grantat step 1202. At step 1204, the mobile station 100 _(n) receives thePDCCH in subframe #i. At step 1206, if the ID for the user communicatingover the PUSCH in subframe #i+3 matches the ID of the mobile station 100_(n), the mobile station 100 _(n) transmits a PUSCH in subframe #i+3based on the transport format information within the PDCCH, that is,uplink scheduling grant. At step 1208, the base station apparatus 200receives the PUSCH in subframe #i+3 from the mobile station which thebase station apparatus 200 informs that the mobile station shouldcommunicate over the PUSCH in subframe #i+3, and determines that thedecoding has been unsuccessful, that is, determines that the CRC checkresult is NG. In this case, at step 1210, the base station apparatus 200transmits NACK as acknowledgement information to the PUSCH (UL-SCH as atransport channel) to the mobile station 100 _(n). Since the mobilestation 100 _(n) receives the NACK at step 1212, the mobile station 100_(n) transmits a PUSCH at a predefined timing, that is, in subframe #i+9at step 1214. At step 1216, the base station apparatus 200 receives thePUSCH from the mobile station 100 _(n) to which it transmitted the NACK.

As illustrated in FIG. 6B, for example, the base station apparatus 200informs the mobile station 100 _(n) in a PDCCH in subframe #i of an IDfor a user communicating over a PUSCH in #i+3 subframe and/or transportformat information for the user data, that is, uplink scheduling grantat step 1222. At step 1224, the mobile station 100 _(n) receives thePDCCH in subframe #i. At step 1226, if the ID for the user communicatingover the PUSCH in subframe #i+3 matches the ID of the mobile station 100_(n), the mobile station 100 _(n) transmits the PUSCH in subframe #i+3based on the transport format information in the PDCCH, that is, theuplink scheduling grant. At step 1228, the base station apparatus 200receives the PUSCH in subframe #i+3 from the mobile station 100 _(n)which the base station apparatus 200 informs that the mobile station 100_(n) should communicate over the PUSCH and determines that the decodinghas been unsuccessful, that is, determines that the CRC check result isNG. In this case, at step 1230, the base station apparatus 200 transmitsa NACK as acknowledgement information (UL-SCH as a transport channel) tothe mobile station 100 _(n). If the mobile station 100 _(n) erroneouslydetermines the NACK as ACK at step 1232, the mobile station 100 _(n)does not transmit the PUSCH in subframe #i+9 at step 1234. As a result,the base station apparatus 200 would not also receive the PUSCH insubframe #i+9 from the mobile station 100 _(n) at step 1236. Thus, thebase station apparatus 200 could conduct power determination (powerdetection) of the uplink shared channel by checking the datademodulation reference signal at steps 1216 and 1236.

In addition, as will be illustrated with reference to FIG. 7, thebaseband signal processing unit 208 makes the power determination for apredefined portion of the received signal and determines whether themobile station 100 _(n) has actually transmitted acknowledgementinformation. A transmission operation of MAC retransmission control isperformed based on the determination. An exemplary case where the PUSCHis not transmitted from the mobile station 100 _(n) in a subframe andacknowledgement information is transmitted is described below. In thiscase, the acknowledgement information is transmitted in a PUCCH being acontrol channel frequency-multiplexed with the PUSCH.

FIG. 7 illustrates the above-mentioned operations of the mobile station100 _(n) and the base station apparatus 200 from a temporal viewpoint.As illustrated in FIG. 7A, for example, the base station apparatus 200informs the mobile station 100 _(n) over a PDCCH in subframe #i of an IDfor a user communicating over a PDSCH in subframe #i and/or transportformat information for the user data, that is downlink schedulinginformation at step 1102. At step 1102, the base station apparatus 200also transmits a PDSCH corresponding to the downlink schedulinginformation to the mobile station 100 _(n) in subframe #i. At step 1104,the mobile station 100 _(n) receives the PDCCH in subframe #i. At step1104, if the ID for the user communicating over the PDSCH in subframe #iwithin the PDCCH matches the ID of the mobile station 100 _(n), themobile station 100 _(n) receives the PDSCH based on the transport formatinformation in the PDCCH, that is, downlink scheduling information. Atstep 1106, the mobile station 100 _(n) transmits acknowledgementinformation over an uplink control channel PUCCH in subframe #i+3 basedon the CRC check result at reception of the PDSCH at step 1104. At step1108, the base station apparatus 200 receives the acknowledgementinformation from the mobile station 100 _(n) which the base stationapparatus 200 informs at step 1102 that the mobile station 100 _(n)should communicate over the PDSCH in subframe #i.

As illustrated in FIG. 7B, if the mobile station 100 _(n) fails toreceive the PDCCH transmitted (1112) from the base station apparatus 200at step 1114, the mobile station 100 _(n) does not receive the PDSCH andthus does not transmit acknowledgement information based on the CRCcheck result at reception of the PDSCH in subframe #i+3 at step 1116.Accordingly, the base station apparatus 200 also would not receive thePUCCH in subframe #i+3 from the mobile station 100 _(n) at step 1118. Asa result, the base station apparatus 200 can make a SIR determinationfor the acknowledgement information by checking the data demodulationreference signal at steps 1108 and 1118. In other words, the basestation apparatus can determine whether the mobile station 100 _(n) hasactually transmitted the acknowledgement information. Furthermore, thebase station apparatus 200 can determine whether the mobile station 100_(n) has received downlink scheduling information.

The call processing unit 210 performs call operations such ascommunication channel setting or release, management of states of theradio base station 200 and/or radio resources.

An exemplary arrangement of the baseband signal processing unit 208 isdescribed with reference to FIG. 8A.

As illustrated in FIG. 8A, the baseband signal processing unit 208includes a layer 1 processing unit 2081, a MAC processing unit 2082 anda RLC processing unit 2083.

The layer 1 processing unit 2081, the MAC processing unit 2082 in thebaseband signal processing unit 208, and the call processing unit 210are coupled to each other.

The layer 1 processing unit 2081 performs channel coding and IFFToperations on shared channels transmitted in downlinks, receptionoperations, such as FFT and IDFT operations on shared channelstransmitted in uplinks and channel decoding.

The layer 1 processing unit 2081 receives from the MAC processing unit2082 an ID for a user communicating over a PDSCH and/or transport formatinformation for the user data, that is, downlink scheduling information,and an ID for a user communicating over a PUSCH and/or transport formatinformation for the user data, that is, uplink scheduling grant. Also,the layer 1 processing unit 2081 performs transmission operations suchas channel coding and IFFT on the ID for the user communicating over thePDSCH and/or the transport format information for the user data, thatis, the downlink scheduling information, and the ID for the usercommunicating over the PUSCH and/or the transport format information forthe user data, that is, the uplink scheduling grant. The ID for the usercommunicating over the PDSCH and/or the transport format information forthe user data, that is, the downlink scheduling information, and the IDfor the user communicating over the PUSCH and/or the transport formatinformation for the user data, that is, the uplink scheduling grant, aremapped into a PDCCH being a downlink control channel.

Also, the layer 1 processing unit 2081 demodulates and decodesacknowledgement information and CQI mapped into transmitted uplinkcontrol channels. If the layer 1 processing unit 2081 receives theacknowledgement information or the CQI for a mobile station that doesnot transmit user data in the subframe when the acknowledge informationor the CQI is transmitted in uplinks, the layer 1 processing unit 2081receives the acknowledgement information or the CQI mapped into PUCCHsplaced at both ends of a system frequency band. Then, the layer 1processing unit 2081 transmits the received acknowledgement informationor CQI to the MAC processing unit 2082. The acknowledgement informationconsists of either of ACK, NACK or DTX, and the notation “DTX” meansthat the mobile station 100 _(n) has not actually transmitted theacknowledgement information. A DTX determination method, that is, adetermination method of determining whether the mobile station 100 _(n)has actually transmitted the acknowledgement information is describedbelow. The CQI is transmitted after performing reliability determinationof the CQI as described below. In other words, only CQIs with higherreliability are transmitted to the MAC processing unit 2082 while CQIswith lower reliability are not transmitted to the MAC processing unit2082.

As described with reference to FIG. 5 or FIG. 6, if the mobile station100 _(n) has not properly received the PDCCH into which the ID for theuser communicating over the PUSCH or the transport format informationfor the user data is mapped or if the mobile station 100 _(n) haserroneously determined NACK transmitted as the acknowledgementinformation to the uplink shared channel as ACK, the mobile station 100_(n) does not transmit the uplink shared channel. In this embodiment,the base station apparatus 200 determines whether the mobile station 100_(n) has actually transmitted the uplink shared channel throughreception operations such as FFT or IDFT operations on the transmitteduplink shared channel and channel decoding.

The layer 1 processing unit 2081 determines whether the mobile station100 _(n) has actually transmitted the uplink shared channel in asubframe to be used by the mobile station 100 _(n) to transmit theuplink shared channel. For example, the layer 1 processing unit 2081measures a SIR of a data demodulation reference signal in the PUSCH tobe transmitted, and if the SIR is higher than a predefined threshold,the layer 1 processing unit 2081 may determine that the mobile station100 _(n) has actually transmitted the uplink shared channel. On theother hand, if the SIR is lower than or equal to the predefinedthreshold, the layer 1 processing unit 2081 may determine that themobile station 100 _(n) has not actually transmitted the uplink sharedchannel. In general, it may be determined based on comparison betweenquality of received signals and a threshold whether the PUSCH has beentransmitted. Then, the layer 1 processing unit 2081 transmits results ofpower determination for the PUSCH to the MAC processing unit 2082.

The quality of received signals may be any value as long as it is ameasure indicative of the quality of received signals such as theabove-mentioned SIR and a reception level.

Also, if the layer 1 processing unit 2081 determines in the powerdetermination for the PUSCH that the mobile station 100 _(n) has notactually transmitted the uplink shared channel, the layer 1 processingunit 2081 may transmit an ACK being positive acknowledgement to themobile station 100 _(n), as the acknowledgement information to theuplink shared channel. Some effects of transmitting the ACK to themobile station 100 _(n) are described below. If the UL-SCH powerdetermination is erroneous, that is, if the mobile station 100 _(n) hasactually transmitted the PUSCH (UL-SCH) but the base station apparatus200 erroneously determines that the mobile station 100 _(n) has nottransmitted it, the mobile station 100 _(n) continues retransmission. Onthe other hand, the base station apparatus 200 may sometimes assignresource blocks used by the mobile station 100 _(n) for theretransmissions to a new transmission by another mobile station (forexample, mobile station 100 _(m), (m≠n)). In this case, theretransmission by the mobile station 100 _(n) may conflict with the newtransmission by the mobile station 100 _(m), which may significantlydegrade characteristics of both the retransmission by the mobile station100 _(n) and the new transmission by the mobile station 100 _(m). Asmentioned above, in the case where the positive acknowledgement ACK istransmitted as the acknowledgement information to the PUSCH (UL-SCH) forwhich it is determined that the mobile station 100 _(n) has not actuallytransmitted the uplink shared channel, the mobile station 100 _(n) couldbe caused to stop the retransmission even if the mobile station 100 _(n)has actually transmitted the PUSCH (UL-SCH), which may prevent theabove-mentioned collision.

In the above-mentioned embodiment, the layer 1 processing unit 2081makes the power determination based on the SIR of the data demodulationreference signal in the PUSCH to be transmitted. In other embodiments,in addition to the SIR of the data demodulation reference signal in thePUSCH to be transmitted, the power determination may be made based onthe SIR of a data signal in the PUSCH to be transmitted. It is possibleto improve accuracy of the power determination by using the SIRs of boththe reference signal and the data signal.

Alternatively, the power determination may be made based on only the SIRof the data signal in the PUSCH to be transmitted rather than the SIR ofthe data demodulation reference signal in the PUSCH to be transmitted.

The threshold may be set based on transmit power of the mobile station100 _(n). The transmit power of the mobile station 100 _(n) may betransmitted to the mobile station 100 _(n) as one information item inthe uplink scheduling grant in the PDCCH, for example. Alternatively,the transmit power of the mobile station 100 _(n) may be transmitted tothe mobile station 100 _(n) in association with payload size (data size)being one information item in the uplink scheduling grant. Theassociation of the transmit power with the payload size means thatcorrespondence between the transmit power and the payload size ispredefined between the mobile station 100 _(n) and the base stationapparatus 200. More specifically, a greater threshold may be set if thetransmit power is higher while a smaller threshold may be set if thetransmit power is lower.

Alternatively, the threshold may be set based on power differencebetween the uplink shared channel and the sounding reference signal.More specifically, a greater threshold may be set if the powerdifference between the uplink shared channel and the sounding referencesignal is larger while a smaller threshold may be set if the powerdifference between the uplink shared channel and the sounding referencesignal is smaller.

Alternatively, the threshold may be set based on the modulation schemefor the uplink shared channel, for example. More specifically, a greaterthreshold may be set if the modulation scheme is 16 QAM while a smallerthreshold may be set if the modulation scheme is QPSK.

Alternatively, the threshold may be set based on MCS (Modulation andScheme) level for the uplink shared channel. More specifically, agreater threshold may be set if the MCS level is higher while a smallerthreshold may be set if the MCS level is lower. The MCS level may bedefined based on at least one of a modulation scheme, a data size,transmit power, a required SIR and the amount of frequency resources.

Alternatively, the threshold may be set based on the amount of frequencyresources for the PUSCH to be transmitted, that is, a transmit bandwidthor the number of resource blocks. More specifically, a greater thresholdmay be set if the amount of frequency resources is larger while asmaller threshold may be set if the amount of frequency resources issmaller. In this embodiment, information regarding the frequencyresources for the PUSCH to be transmitted, that is, informationregarding the resource blocks, may be transmitted to a mobile station ina form of frequency resource assignment information or resource blockassignment information being one information item in uplink schedulinggrant within a PDCCH, for example. For a larger amount of frequencyresources, power determination can be made with higher accuracy. On theother hand, if the power determination is false, the involved impactwould be significant, and thus the power determination must be performedmore rigorously. In contrast, for a smaller amount of frequencyresources, the power determination cannot be made with insufficientaccuracy. On the other hand, if the power determination is false, theinvolved impact would be insignificant, and thus the power determinationmust be performed less rigorously than the case of the larger amount offrequency resources. In order to satisfy such requirements, it may beadvantageous to set the threshold for the power determination based onthe amount of frequency resources for the PUSCH, that is, the transmitbandwidth or the number of resource blocks.

An exemplary arrangement of the layer 1 processing unit 2081 isdescribed in detail with reference to FIG. 8B. The layer 1 processingunit 2081 includes a CP removal unit 208102, a FFT unit 208104, asubcarrier demapping unit 208106, a demultiplexer (DEMUX) unit 208108, achannel estimation unit 208109, frequency equalization units208110A-208110C, IDFT units 208112A-208112C, a PUSCH (UL-SCH) decodingunit 208114A, a PUCCH (ACK/NACK) decoding unit 208114B, a PUCCH (CQI)decoding unit 208114C, a signal power estimation unit 208116A, aninterference power estimation unit 208118A, a SIR computation unit208120A, a PUSCH power determination unit 208122A and a thresholdsetting unit 208124A.

The CP removal unit 208102 removes an attached CP portion from an uplinkbaseband signal incoming from the transmitting and receiving unit 206 ata predefined timing and supplies the resulting signal to the FFT unit208104.

The FFT unit 208104 converts the whole system bandwidth from temporaldomain signals into frequency domain signals through Fast FourierTransform and supplies the converted signals to the subcarrier demappingunit 208106.

The subcarrier demapping unit 208106 restores demapped subcarriers intoa multiplexed signal, and the demultiplexer 208108 segments themultiplexed signal into certain blocks. Signals for uplink sharedchannels are supplied to the frequency equalization unit 208110A.Acknowledgement information mapped into PUCCHs is supplied to thefrequency equalization unit 208110B. CQIs mapped into PUCCHs aresupplied to the frequency equalization unit 208110C. Demodulationreference signals in the PUCCHs or the uplink shared channels aresupplied to the channel estimation unit 208109.

The frequency equalization unit 208110A performs reception operations inaccordance with channel compensation (restore phases turned intransmission into original transmit states) using channel estimationvalues from the channel estimation unit 208109. The resulting signalsfor uplink shared channels are decoded at the IDFT unit 208112A and thePUSCH (UL-SCH) decoding unit 208114A.

Signals subjected to IDFT processing at the IDFT unit 208112A aresupplied to the signal power estimation unit 208116A and theinterference power estimation unit 208118A.

The frequency equalization unit 208110B performs reception operations inaccordance with channel compensation (restore phases turned intransmission into original transmit states) using channel estimationvalues from the channel estimation unit 208109. The resulting signalsfor acknowledgement information mapped into control channels are decodedat the IDFT unit 208112B and the PUCCH (ACK/NACK) decoding unit 208114B.

The frequency equalization unit 208110C performs reception operations inaccordance with channel compensation (restore phases turned intransmission into original transmit states) using channel estimationvalues from the channel estimation unit 208109. The resulting signalsfor the CQIs mapped into control channels are decoded at the IDTF unit208112C and the PUCCH (ACK/NACK) decoding unit 208114C.

The channel estimation unit 208109 derives the channel estimation valuesfrom uplink demodulation reference signals generated at thedemultiplexer 208108. The channel estimation values are supplied to thefrequency equalization units 208110A-208110C.

The signal power estimation unit 208116A derives a signal power level ofthe IDFT processed uplink shared channel supplied from the IDFT unit208112A and supplies the derived signal power level to the SIRcomputation unit 208120A.

The interference power estimation unit 208116A derives an interferencepower level of a frequency band for transmitting the IDFT processeduplink shared channel supplied from the IDFT unit 208112A and suppliesthe derived interference power level to the SIR computation unit208120A.

The SIR computation unit 208120A derives a SIR based on the signal powerlevel received from the signal power estimation unit 208116A and theinterference power level received from the interference power estimationunit 208118A and supplies the derived SIR to the PUSCH powerdetermination unit 208122A.

The PUSCH power determination unit 208122A determines whether a mobilestation has actually transmitted the uplink shared channel PUSCH basedon comparison between the SIR supplied from the SIR computation unit208120A and a threshold supplied from the threshold setting unit208124A. In other words, the PUSCH power determination unit 208122Amakes the determination as to whether the mobile station 100 _(n) hasactually transmitted the uplink shared channel as described above inconjunction with the layer 1 processing unit 2081 and performsoperations for (1) UL-SCH power determination method as described below.The PUSCH power determination unit 208122A transmits to the MACprocessing unit 2082 the determination result as to whether the mobilestation has actually transmitted the uplink shared channel PUSCH.

Also, if the PUSCH power determination unit 208122A determines that themobile station 100 _(n) has not actually transmitted the uplink sharedchannel, the PUSCH power determination unit 208122A may determine thatpositive response ACK should be transmitted to the mobile station 100_(n) as acknowledgement information to the uplink shared channel. Inthis case, for example, the determination result that the positiveresponse ACK should be transmitted to the mobile station 100 _(n) istransmitted to the MAC processing unit 2082, which may performtransmission operations on the positive response ACK as a part of HARQoperations. Alternatively, the determination result that the positiveresponse ACK should be transmitted to the mobile station 100 _(n) istransmitted from the PUSCH power determination unit 208122A to atransmission operation executing part in the layer 1 processing unit2081, which may perform transmission operations on the positive responseACK.

The threshold setting unit 208124A sets a threshold used for thedetermination at the PUSCH power determination unit 208122A andtransmits the threshold to the PUSCH power determination unit 208122A.

In this embodiment, the threshold setting unit 208124A may set thethreshold based on transmit power for use in the mobile station, asmentioned above. Alternatively, the threshold setting unit 208124A mayset the threshold based on a modulation scheme for the uplink sharedchannel, as mentioned above. Alternatively, the threshold setting unit208124A may set the threshold based on the MCS level for the uplinkshared channel, as mentioned above. Alternatively, the threshold settingunit 208124A may set the threshold based on the amount of frequencyresources for the uplink shared channel, as mentioned above.Alternatively, the threshold setting unit 208124A may set the thresholdbased on power difference between the uplink shared channel and asounding reference signal, as mentioned above.

In this manner, the layer 1 processing unit 2081 in the base stationapparatus 200 determines whether a mobile station has actuallytransmitted the PUSCH through the power determination for the PUSCH. Thedetermination as to whether a mobile station has actually transmittedthe PUSCH makes it possible to determine whether the mobile station hassuccessfully received uplink scheduling grant within a PDCCH oracknowledgement information to the PUSCH within the PDCCH, asillustrated in FIGS. 5 and 6.

Also as illustrated with reference to FIG. 7, if a mobile station failedto receive an ID for a user communicating over a downlink shared channeland/or transport format information for the user data, that is, a PDCCHinto which the downlink scheduling information is mapped, the mobilestation does not receive the PDSCH and thus does not transmit theacknowledgement information at a predefined timing. In this embodiment,the layer 1 processing unit 2081 determines whether a mobile station hasactually transmitted the acknowledgement information. Also in thisembodiment, it is assumed that the PUSCH is not transmitted from amobile station at a subframe and the acknowledgement information istransmitted instead. In other words, the case where the acknowledgementinformation is transmitted over a control channel PUCCHfrequency-multiplexed with the PUSCH is described below.

The layer 1 processing unit 2081 determines whether the mobile station100 _(n) has actually transmitted the acknowledgement information in asubframe to transmit the acknowledgement information in a PUCCH. Forexample, the layer 1 processing unit 2081 measures a SIR for a datademodulation reference signal in the PUCCH into which theacknowledgement information may be mapped. If the SIR is higher than apredefined threshold, the layer 1 processing unit 2081 may determinethat the mobile station 100 _(n) has actually transmitted theacknowledgement information. On the other hand, if the SIR is lower thanthe predefined threshold, the layer 1 processing unit 2081 may determinethat the mobile station 100 _(n) has not actually transmitted theacknowledgement information. In general, the determination may be madethrough comparison between quality of a received signal and thethreshold. For the quality of a received signal, any measure such as theabove-mentioned SIR or receive level may be used as long as it indicatesthe quality of the received signal. Then, the layer 1 processing unit2081 transmits a result of power determination on the acknowledgementinformation to the MAC processing unit 2082. Note that the determinationas to whether the mobile station 100 _(n) has actually transmitted theacknowledgement information is applicable even in any of the cases whereonly the acknowledgement information is transmitted, the acknowledgementinformation and CQI are multiplexed with each other and transmitted, andother control information items such as a scheduling request and arelease request are multiplexed with each other and transmitted. Inthese cases, different thresholds may be set. Also, even if a jointcoding scheme to encode the acknowledgement information and the CQItogether is applied to multiplex the acknowledgement information withthe CQI or even if a separate coding scheme to encode theacknowledgement information and the CQI separately is applied tomultiplex the acknowledgement information with the CQI, theabove-mentioned determination as to whether the mobile station 100 _(n)has actually transmitted the acknowledgement information is stillapplicable.

In the case where only the acknowledgement information is transmitted,for example, the acknowledgement information may be transmitted in anyof resources A illustrated in FIG. 13. Also in the case where theacknowledgment information and the CQI are multiplexed with each otherand transmitted, for example, they may be transmitted in any ofresources B illustrated in FIG. 13. Multiple resources are multiplexedin FIG. 13, but any of multiplexing schemes such as CDM, block spreadingmultiplexing, frequency multiplexing, time multiplexing or anycombination thereof may be applied. In addition, the CDM may includeWalsh CDM and CAZAC sequence CDM, for example.

For example, a threshold used for the power determination in the case oftransmission of the multiplexed acknowledgement and the CQI may be setto be greater than that in the case of transmission of only theacknowledgement information. More specifically, in the case oftransmission of the multiplexed acknowledgement information and CQI, ifa mobile station has failed to successfully receive a PDCCH transmitted(1112) by the base station apparatus 200 (1114), the mobile stationwould transmit only the CQI. In this case, the layer 1 processing unit2081 has to determine a difference between the power in the transmissionof only the CQI and the power in the transmission of the multiplexedacknowledgement information and CQI. To this end, a greater thresholdwould be set than that for the power determination in the transmissionof only the acknowledgement information.

In this embodiment, the layer 1 processing unit 2081 makes the powerdetermination based on the SIR for the data demodulation referencesignal in the PUCCH to be transmitted. In other embodiments, in additionto the SIR for the data demodulation reference signal in the PUCCH to betransmitted, the layer 1 processing unit 2081 may make the powerdetermination based on the acknowledgement information to be transmittedor the SIR of a signal sequence of the multiplexed acknowledgementinformation and the CQI if the CQI is multiplexed. By using both the SIRof the reference signal and the SIR of the signal sequence of theacknowledgement information and the CQI, the accuracy of the powerdetermination can be improved.

Alternatively, the power determination may be made based on theacknowledgement information to be transmitted or only the SIR for thesignal sequence of the multiplexed acknowledgement information and CQIif the CQI is multiplexed rather than the SIR for the data demodulationreference signal in the PUCCH to be transmitted.

An exemplary arrangement of the layer 1 processing unit 2081 isdescribed in detail with reference to FIG. 8C. The layer 1 processingunit 2081 includes a CP removal unit 208102, a FFT unit 208104, asubcarrier demapping unit 208106, a demultiplexer (DEMUX) unit 208108, achannel estimation unit 208109, frequency equalization units208110A-208110C, IDFT units 208112A-208112C, a PUSCH (UL-SCH) decodingunit 208114A, a PUCCH (ACK/NACK) decoding unit 208114B, a PUCCH (CQI)decoding unit 208114C, a signal power estimation unit 208116B, aninterference power estimation unit 208118B, a SIR computation unit208120B, a PUCCH power determination unit 208126B and a thresholdsetting unit 208124B.

The components other than the IDFT unit 208112B, the signal powerestimation unit 208116B, the interference power estimation unit 208118B,the SIR computation unit 208120B, the PUCCH power determination unit208126B and the threshold setting unit 208124B are the same as those inFIG. 8B and thus are not repeatedly described.

The IDFT unit 208112B performs IDFT on signals subjected to receptionoperations through channel compensation at the frequency equalizationunit 208110B and supplies the resulting signals to the PUCCH (ACK/NACK)decoding unit 208114B. Also, the IDFT unit 208112B supplies the IDFTprocessed signals to the signal power estimation unit 208116B and theinterference power estimation unit 208118B.

The signal power estimation unit 208116B derives a signal power level ofthe IDFT processed uplink control channel received from the IDFT unit208112B and supplies the derived signal power level to the SIRcomputation unit 208120B.

The interference power estimation unit 208116B derives an interferencepower level after the IDFT processing of a frequency band fortransmitting the uplink control channel received from the IDFT unit208112B and supplies the derived interference power level to the SIRcomputation unit 208120B.

The SIR computation unit 208120B derives a SIR based on the signal powerlevel supplied from the signal power estimation unit 208116B and theinterference power level supplied from the interference power estimationunit 208118B and supplies the derived SIR to the PUCCH powerdetermination unit 208126B.

The PUCCH power determination unit 208126B determines whether a mobilestation has actually transmitted acknowledgement information over aPUCCH based on comparison between the SIR supplied from the SIRcomputation unit 208120B and a threshold supplied from the thresholdsetting unit 208124B. In other words, the PUCCH power determination unit208126B determines whether the mobile station 100 _(n) has actuallytransmitted the acknowledgement information as described in conjunctionwith the layer 1 processing unit 2081 and (2) performs receptionoperations of HARQ ACK. The PUCCH power determination unit 208126Btransmits the determination result to the MAC processing unit 2082.

The threshold setting unit 208124B sets a threshold used for thedetermination at the PUCCH power determination unit 208126B andtransmits the threshold to the PUCCH power determination unit 208126B.

The operations as described with reference to FIG. 8C may be applied tothe case of transmission of only the acknowledgement information overthe PUCCH or to the case of transmission of the multiplexedacknowledgement information downlink radio quality information CQI.

In this manner, the layer 1 processing unit 2081 in the base stationapparatus 200 determines whether a mobile station has actuallytransmitted the acknowledgement information through the powerdetermination for the acknowledgement information to the downlink sharedchannel in the PUCCH. The determination as to whether the mobile stationhas actually transmitted the acknowledgement information makes itpossible to determine whether the mobile station has successfullyreceived downlink scheduling information within the PDCCH, asillustrated in FIG. 7.

Also, the layer 1 processing unit 2081 performs reception operations onthe CQI mapped into the PUCCH placed at both ends of the system band ifthe CQI is received for a mobile station that does not receive user datain uplinks in a subframe. At this time, the layer 1 processing unit 2081may determine reliability of the CQI. In other words, the layer 1processing unit 2081 measures a SIR of a sequence of received bits forthe CQI in a PUCCH into which the CQI is mapped. If the SIR is higherthan a predefined threshold, the layer 1 processing unit 2081 determinesthat the received CQI reliability is high, and on the other hand, if theSIR is lower than or equal to the predefined threshold, the layer 1processing unit 2081 determines that the received CQI reliability islow. In general, the received CQI reliability may be determineddepending on comparison between quality of received signals and athreshold. The quality of received signals may be any measure such asthe SIR and a receive level as long as the measure indicates quality ofthe received signals. In this embodiment, the SIR of the sequence ofreceived bits for the CQI may be for a bit sequence with the maximumcorrelation value, that is, a bit sequence with the maximum likelihoodwithin the CQI bit sequence. Alternatively, the layer 1 processing unit2081 may measure the SIR for a data demodulation reference signal in thePUCCH into which the CQI is mapped. Alternatively, the layer 1processing unit 2081 may measure both the SIR for the data demodulationreference signal in the PUCCH into which the CQI is mapped and the SIRfor the sequence of received bits for the CQI in the PUCCH into whichthe CQI is mapped. In this embodiment, as a result of the determinationof the CQI reliability, the layer 1 processing unit 2081 may transmitonly the CQI with high reliability to the MAC processing unit 2082 anddoes not transmit the CQI with insufficient reliability to the MACprocessing unit 2082. In this case, the CQI with insufficientreliability would not be used in scheduling and AMC.

When the reliability is determined, the layer 1 processing unit 2081 maydetermine whether a mobile station has actually transmitted the CQI. Ifthe layer 1 processing unit 2081 determines that the mobile station hasnot actually transmitted the CQI, the layer 1 processing unit 2081 maydetermine that an uplink of the mobile station is out ofsynchronization.

An exemplary arrangement of the layer 1 processing unit 2081 isdescribed in detail with reference to FIG. 8D. The layer 1 processingunit 2081 includes a CP removal unit 208102, a FFT unit 208104, asubcarrier demapping unit 208106, a demultiplexer (DEMUX) unit 208108, achannel estimation unit 208109, frequency equalization units208110A-208110C, IDFT units 208112A-208112C, a PUSCH (UL-SCH) decodingunit 208114A, a PUCCH (ACK/NACK) decoding unit 208114B, a PUCCH (CQI)decoding unit 208114C, a signal power estimation unit 208116C, aninterference power estimation unit 208118C, a SIR computation unit208120C, a PUCCH power determination unit 208126C and a thresholdsetting unit 208124C.

The components other than the IDFT unit 208112C, the signal powerestimation unit 208116C, the interference power estimation unit 208118C,the SIR computation unit 208120C, the PUCCH power determination unit208126C and the threshold setting unit 208124C are the same as those inFIG. 8B and thus are not repeatedly described.

The IDFT unit 208112C performs IDFT on signals subjected to receptionoperations through channel compensation at the frequency equalizationunit 208110C and supplies the resulting signals to the PUCCH (ACK/NACK)decoding unit 208114C. Also, the IDFT unit 208112C supplies the IDFTprocessed signals to the signal power estimation unit 208116C and theinterference power estimation unit 208118C.

The signal power estimation unit 208116C derives a signal power level ofthe IDFT processed uplink control channel received from the IDFT unit208112C and supplies the derived signal power level to the SIRcomputation unit 208120C.

The interference power estimation unit 208118B derives an interferencepower level for the IDFT processed signals of a frequency band fortransmitting the uplink control channel received from the IDFT unit208112C and supplies the derived interference power level to the SIRcomputation unit 208120C.

The SIR computation unit 208120C derives a SIR based on the signal powerlevel supplied from the signal power estimation unit 208116C and theinterference power level supplied from the interference power estimationunit 208118C and supplies the derived SIR to the PUCCH powerdetermination unit 208126C.

The PUCCH power determination unit 208126C determines reliability ofradio quality information CQI for downlinks transmitted from a mobilestation based on comparison between the SIR supplied from the SIRcomputation unit 208120C and a threshold supplied from the thresholdsetting unit 208124C. In other words, the PUCCH power determination unit208126C determines the CQI reliability as described in conjunction withthe layer 1 processing unit 2081 and (3) performs CQI reliabilitydetermination as describe below. The PUCCH power determination unit208126C transmits the determination result of the CQI reliability to theMAC processing unit 2082 pending.

The threshold setting unit 208124C sets a threshold used for thedetermination at the PUCCH power determination unit 208126C andtransmits the threshold to the PUCCH power determination unit 208126C.

The MAC processing unit 2082 receives reception results of theacknowledgement information and the CQI mapped into uplink controlchannels.

The MAC processing unit 2082 performs MAC retransmission control ondownlink user data such as HARQ transmission operations, schedulingoperations, selection operations of transmission formats and frequencyresource assignment operations. The scheduling operation may meanselection of a mobile station that receives user data over a downlinkshared channel in a subframe. The selection operation of transmissionformats may mean determination of a modulation scheme, a coding rate anda data size for user data received at the mobile station selected in thescheduling operation. The determination of a modulation scheme, a codingrate and a data size may be made based on a CQI transmitted from themobile station in uplinks, for example. In addition, the frequencyresource assignment operation may mean to determine a resource block tobe used for user data received at the mobile station selected in thescheduling operation. The resource block determination may be made basedon the CQI transmitted from the mobile station in uplinks, for example.The MAC processing unit 2082 transmits to the layer 1 processing unit2081 an ID for a user communicating over a PDSCH and/or transport formatinformation for user data, that is, downlink scheduling information,which are determined in the scheduling operation, the transmissionformat selection operation and the frequency resource assignmentoperation.

The MAC processing unit 2082 performs reception operations for the MACretransmission control over uplink user data, scheduling operations,transmission format selection operations, frequency resource assignmentoperations and/or others. The scheduling operation may mean selection ofa mobile station to transmit user data over a shared channel in acertain subframe. The transmission format selection operation means todetermine a modulation scheme, a coding rate and a data size for userdata transmitted from the mobile station selected in the schedulingoperation. The determination of a modulation scheme, a coding rate and adata size may be made based on a SIR, receive power and/or path loss fora sounding reference signal transmitted from the mobile station inuplinks, for example. The frequency resource assignment operation meansto determine a resource block used to transmit user data from the mobilestation selected in the scheduling operation. The resource blockdetermination may be made based on the SIR for the sounding referencesignal transmitted from the mobile station in uplinks, for example.Then, the MAC processing unit 2082 transmits to the layer 1 processingunit 2081 an ID for a user communicating over a PUSCH and/or transportformat information for the user data, that is, uplink scheduling grant,as determined in the scheduling operation, the transport formatselection operation and the frequency resource assignment operation.

The MAC processing unit 2082 receives results of the power determinationfor uplink shared channels from the layer 1 processing unit 2081. If itis determined in the power determination that the mobile station 100_(n) has not actually transmitted the uplink shared channel, the MACprocessing unit 2082 determines that the mobile station 100 _(n) failedto receive the previously transmitted corresponding PDCCH or that themobile station 100 _(n) failed to receive the previously transmittedcorresponding acknowledgement information to the uplink shared channel,the MAC processing unit 2082 releases a retransmission resource assignedto the uplink shared channel. In this embodiment, the releasing of aresource means that the resource is reassigned to an uplink sharedchannel for another mobile station or to another uplink shared channelnewly transmitted from the current mobile station. According to EvolvedUTRA and UTRAN, synchronous HARQ is used in uplinks. Thus, the uplinkshared channel is transmitted from the mobile station to the basestation apparatus 200 at a predefined timing until it is successfullyreceived or until the number of retransmissions reaches a maximum numberof transmissions. On the other hand, if it is determined that the mobilestation 100 _(n) has not actually transmitted the uplink shared channel,all retransmission resources in subframes to be retransmitted in futureare released for the uplink shared channel.

The MAC processing unit 2082 receives results of power determination foracknowledgement information mapped into PUCCHs that arefrequency-multiplexed with PUSCHs and transmitted from the layer 1processing unit 2081. Then, if it is determined as a result of the powerdetermination that the mobile station 100 _(n) has not actuallytransmitted the acknowledgement information, the MAC processing unit2082 determines that the previously transmitted corresponding downlinkshared channel has not been successfully received and retransmitsinformation mapped into the previously transmitted correspondingdownlink shared channel. For example, the MAC processing unit 2082determines that the mobile station 100 _(n) failed to receive not theshared channel but downlink scheduling information in a PDCCH attachedthereto and then assumes the information mapped into the downlink sharedchannel as the previous transmission would be invalid. In other words,if the previous transmission corresponds to the first transmission, thecurrent transmission may be also performed as the first transmission.Also, if the previous transmission corresponds to the secondtransmission, the current transmission may be also performed as thesecond transmission.

Also in the case where the power determination is negative (NACK) forthe acknowledgement information transmitted in a PUCCH where theacknowledgement information is multiplexed with the CQI, the MACprocessing unit 2082 may determine that the corresponding downlinktransmission is invalid and transmit information mapped into thedownlink shared channel. In other words, if the previous transmissioncorresponds to the first transmission, the current transmission may bealso performed as the first transmission. Also, if the previoustransmission corresponds to the second transmission, the currenttransmission may be also performed as the second transmission.

Some reasons why the above-mentioned operations should be performed inthe case where the power determination is negative (NACK) for theacknowledgement information transmitted in the PUCCH is described indetail below. For example, signals for the acknowledgement informationmay be embedded in demodulation reference signals in the PUCCH fortransmitting the CQI as the multiplexing scheme of the acknowledgementinformation and the CQI. In this case, it may appear to the base stationapparatus that the acknowledgement information is always transmittedindependently of whether the mobile station has or has not actuallytransmitted the acknowledgement information. Thus, the base stationapparatus cannot determine whether the mobile station has not receivedthe shared channel or downlink scheduling information successfully. Forthis reason, the corresponding downlink transmission is determined to beinvalid in consideration of unsuccessful reception of downlinkscheduling information at the mobile station, and retransmission of theinformation mapped into downlink shared channels makes it possible toreduce occurrence frequency of events where the mobile station fails toreceive the first transmission.

In the case where the power determination is negative (NACK) for theacknowledgement information transmitted in a PUCCH where theacknowledgement information is multiplexed with the CQI, the MACprocessing unit 2082 does not always retransmit information mapped intothe downlink shared channel as the corresponding downlink transmissionbeing invalid. For the first reception of the NACK, the MAC processingunit 2082 may retransmit the information mapped into the downlink sharedchannel as the corresponding transmission being invalid. For the nextreception of the NACK, the MAC processing unit 2082 may retransmit theinformation mapped into the downlink shared channel as the correspondingdownlink transmission being valid. The fact that the correspondingdownlink transmission is valid means that downlink schedulinginformation is successfully received at a mobile station and signals forthe corresponding shared channel is received at the mobile station. Forthe determination of validity of the corresponding downlink transmissionin the NACK reception, only the first NACK may be determined to beinvalid and subsequent NACKs may be determined to be valid.Alternatively, odd numbered NACKs may be determined to be invalid whileeven numbered NACKS may be determined to be valid.

In addition, if a CQI with lower reliability is not transmitted inaccordance with CQI reliability determination, the MAC processing unit2082 may use the previous CQI as the CQI to be transmitted at thecurrent timing.

The RLC processing unit 2083 performs transmission operations in a RLClayer on downlink packet data such as segmentation and concatenation andtransmission operations for RLC retransmission control and/or receptionoperations in the RLC layer on uplink data such as segmentation andconcatenation and reception operations for the RLC retransmissioncontrol. Also, the RLC processing unit 2083 may further performoperations in a PDCP layer.

[Procedure for Uplink Reception Method]

Next, an exemplary uplink reception method at a base station apparatusis described below. Specifically, three types of uplink receptionmethods as presented below are described: UL-SCH power determinationmethod (uplink shared channel power determination method), HARQ ACKreception method (Acknowledgement information reception method), and CQIreliability determination method.

(1) UL-SCH Power Determination Method

A transmission determination method (UL-SCH power determination method)according to one embodiment of the present invention is described withreference to FIG. 9.

In the UL-SCH power determination method, after UL scheduling grant (anID for a user communicating over a PUSCH and transport formatinformation) is transmitted to the mobile station over a PDCCH, powerdetermination is made as to whether the mobile station actuallytransmits the PUSCH (UL-SCH). In the initial transmission, it isdetected whether a detection error of the UL scheduling grant in thePDCCH causes the PUSCH (UL-SCH) not to be transmitted from the mobilestation. In retransmissions, it is detected whether erroneous detectionof the acknowledgement information NACK to the UL-SCH in the PDCCH asACK causes the PUSCH (UL-SCH) not to be transmitted from the mobilestation UE.

A SIR_(data) is derived from a receive power level DRSP_(data) and aninterference wave level Interference_(data) computed based on DM RS(demodulation reference signal) transmitted from the mobile station,

SIR_(data)=DRSP_(data)/Interference_(data),

where the suffix “data” means that the mobile station makes computationon a frequency band in which the PUSCH (UL-SCH) is transmitted.

An exemplary method of computing the interference wave levelInterference_(data) is described in detail below.

The interference wave level may be an instantaneous interference wavelevel in a relevant subframe or an interference wave level averaged overa longer time period such as 200 ms or 100 ms.

The interference wave level may be computed by averaging variances ofdemodulation reference signals transmitted from all mobile stations orby averaging variances of demodulation reference signals transmittedfrom the relevant mobile station. Alternatively, the interference wavelevel may be computed by averaging variances of sounding referencesignals transmitted from all mobile stations or by averaging variancesof sounding reference signals transmitted from the relevant mobilestation.

Alternatively, the interference wave level may be determined bysubtracting the receive power level of the demodulation reference signalfrom a total uplink receive power level including thermal noise. Also inthis case, the interference wave level may be derived from signalstransmitted from only the relevant mobile station or by averagingsignals transmitted from all mobile stations.

The frequency band to compute the interference wave level may be anexact frequency band in which the PUSCH is transmitted or a frequencyband near the frequency band in which the PUSCH is transmitted. Also,the interference wave level during application of hopping is determinedas an actual average value of the interference wave levels computed intwo frequency bands where the hopping is applied.

Then, the power determination is made based on a DTX threshold Th_(data)and a determination as follows,

if (SIR_(data)<(Th_(data)+Δ_(data))) (S102 in FIG. 9)

-   -   “PUSCH (UL-SCH) has not been transmitted” (S106 in FIG. 9),    -   else        -   “PUSCH (UL-SCH) has been transmitted” (S104 in FIG. 9),            where Δ_(data) is a transmit power related value for a            mobile station, for example, a power difference (power            offset) between the sounding reference signal and the PUSCH.            The power determination can be made based on the transmit            power of the mobile station through the Δ_(data).

The DTX threshold Th_(data) may be set based on the amount of frequencyresources in which the PUSCH is transmitted, that is, the transmitbandwidth or the number of resource blocks. Information on frequencyresources in which the PUSCH is transmitted, that is, information on theresource blocks, is transmitted to a mobile station as frequencyresource assignment information or resource block assignment informationbeing one information item in the uplink scheduling grant in a PDCCH.For a larger amount of frequency resources, the power determination isachieved with high accuracy but has to be strictly made due to greatersignificance caused by the erroneous power determination. On the otherhand, for a smaller amount of frequency resources, the powerdetermination cannot be achieved with high accuracy but does not have tobe strictly made due to less significance caused by the erroneous powerdetermination compared to the larger amount of frequency resources. Inorder to satisfy the requirement, it is advantageous to determine theDTX threshold Th_(data) based on the amount of frequency resources forthe PUSCH, that is, the transmit bandwidth or the number of resourceblocks.

If it is determined in the UL-SCH power determination that the PUSCH(UL-SCH) has not been transmitted, the process where non-transmission ofthe PUSCH (UL-SCH) from the relevant mobile station has been detected isreleased (S108 in FIG. 9). The term “releasing of process” herein meansthat it is determined that the mobile station does not transmit thePUSCH (UL-SCH) in that process. In other words, the mobile stationdetermines that it has no data to be retransmitted.

In addition, retransmission resources to be assigned to the PUSCH arereleased at the same time. The term “releasing of resources” hereinmeans that these resources are assigned to uplink shared channels forother mobile stations or that the resources are assigned to uplinkshared channels to be newly transmitted for the relevant mobile station.Also, since synchronous HARQ is used in uplinks in accordance with theEvolved UTRA and UTRAN, uplink shared channels are transmitted from therelevant mobile station to a base station apparatus at predefinedtimings until the uplink shared channels are successfully received oruntil the maximum number of retransmission is reached. If it isdetermined that the mobile station 100 _(n) has not actually transmittedthe uplink shared channels, retransmission resources are released in allsubsequent subframes to be retransmitted for the uplink shared channels.

Furthermore, at the same time (S108 in FIG. 9), the base stationapparatus may transmit a positive response ACK to the relevant mobilestation as acknowledgement information to the PUSCH (UL-SCH) determinedas not being transmitted in the UL-SCH power determination. Some effectsof the transmission of the ACK to the mobile station is described below.If a determination error occurs in the UL-SCH power determination, thatis, if the mobile station has actually transmitted the PUSCH (UL-SCH)but the base station apparatus has determined that the PUSCH has notbeen transmitted, the mobile station continues on retransmissions, andon the other hand, the base station apparatus may assign resource blocksfor the retransmissions from the mobile station to new transmissions forother mobile stations. In this case, the retransmissions from the mobilestation conflict with the new transmissions from the other mobilestations, and thus both characteristics of the retransmissions from themobile station and the new transmissions from the other mobile stationsmay be significantly degraded. As stated above, if the positive responseACK is transmitted as the acknowledgement information to the PUSCH(UL-SCH) determined as not being transmitted, the mobile station stopsthe retransmission regardless of the actual transmissions of the PUSCH(UL-SCH), and thus the above-mentioned conflict may not occur.

(2) HARQ ACK Reception Method

An acknowledgement information determination method (HARQ ACK receptionmethod) according to one embodiment of the present invention isdescribed with reference to FIG. 10.

A HARQ-ACK for the DL-SCH (acknowledgement information for a downlinkshared channel) is mapped into a PUCCH frequency-multiplexed with aPUSCH as illustrated in FIG. 2. A determination of three values is madefor the HARQ-ACK for the DL-SCH (acknowledgement information fordownlink shared channels) in accordance with methods as presented below.

(2-1) Case of Transmission of Only ACK

A SIR_(ACK) is derived from a receive power level DRSP_(ACK) for ademodulation reference signal in a relevant subframe and an interferencewave level Interference_(ACK) computed based on DM RS (demodulationreference signal) transmitted from the relevant mobile station,

SIR_(ACK1)=DRSP_(ACK)/Interference_(ACK),

where the suffix “ACK1” means that the SIR, the receive level for thedemodulation reference signal and the interference wave level arederived for a signal to transmit acknowledgement information to adownlink shared channel from the mobile station.

An exemplary method of computing the interference wave levelInterference_(ACK) is described in detail below.

The interference wave level may be an instantaneous interference wavelevel in the relevant subframe or an interference wave level averagedover a longer time period such as 200 ms or 100 ms.

The interference wave level may be computed by averaging variances ofdemodulation reference signals transmitted from all mobile stations orby averaging variances of demodulation reference signals transmittedfrom the relevant mobile station.

Alternatively, the interference wave level may be determined bysubtracting the receive power level of the demodulation reference signalfrom a total uplink receive power level including thermal noise. Also inthis case, the interference wave level may be derived from signalstransmitted from only the relevant mobile station or by averagingsignals transmitted from all mobile stations.

The frequency band to compute the interference wave level may be anexact frequency band in which a PUCCH is transmitted or a frequency bandnear the frequency band in which the PUCCH is transmitted. Also, theinterference wave level during application of hopping is determined asan actual average value of the interference wave levels computed in twofrequency bands where the hopping is applied.

Then, the three values (ACK/NACK/DTX) determination is made based on aDTX threshold Th_(DTX) _(—) _(ACK1) and a determination as follows,

if (SIR_(ACK1)<Th_(DTX) _(—) _(ACK1)) (S202 in FIG. 10) “DTX has beentransmitted” (S206 in FIG. 10), else “ACK or NACK has been transmitted”(S204 in FIG. 10),where the determination of ACK/NACK is made from signs of a signalsequence of the HARQ-ACK for a downlink (acknowledgement information ofa downlink shared channel).

If it is determined that the DTX has been transmitted, the base stationapparatus retransmits a downlink shared channel (S208 in FIG. 10). Forexample, the base station apparatus may determine that the mobilestation 100 _(n) fails to receive not a shared channel but downlinkscheduling information in the accompanying PDCCH. In this case, the basestation apparatus may determine the previous transmission to be invalidand retransmit information mapped into a downlink shared channel. Inother words, if the previous transmission is the first one, the currenttransmission is processed as the first transmission. If the previoustransmission is the second one, the current transmission may be alsohandled as the second one.

(2-2) Case Where ACK is Multiplexed with CQI, Scheduling Request and/orRelease Request

A SIR_(ACK+CQI) is derived from a receive power level DRSP_(ACK+CQI) fora demodulation reference signal in a relevant subframe and aninterference wave level Interference_(CQI) computed based on DM RS(demodulation reference signal) transmitted from the relevant mobilestation,

SIR_(ACK+CQI)=DRSP_(ACK+CQI)/Interference_(CQI),

where the suffixes “ACK+CQI” and “CQI” mean that the SIR, the receivelevel for the demodulation reference signal and the interference wavelevel are derived for a signal transmitted from the mobile station whereacknowledgement information is multiplexed with the CQI.

An exemplary method of computing the interference wave levelInterference_(CQI) is described in detail below.

The interference wave level may be an instantaneous interference wavelevel in the relevant subframe or an interference wave level averagedover a longer time period such as 200 ms or 100 ms.

The interference wave level may be computed by averaging variances ofdemodulation reference signals transmitted from all mobile stations orby averaging variances of demodulation reference signals transmittedfrom the relevant mobile station.

Alternatively, the interference wave level may be determined bysubtracting the receive power level of the demodulation reference signalfrom a total uplink receive power level including thermal noise. Also inthis case, the interference wave level may be derived from signalstransmitted from only the relevant mobile station or by averagingsignals transmitted from all mobile stations.

The frequency band to compute the interference wave level may be anexact frequency band in which a PUCCH is transmitted or a frequency bandnear the frequency band in which the PUCCH is transmitted. Also, theinterference wave level during application of hopping is determined asan actual average value of the interference wave levels computed in twofrequency bands where the hopping is applied.

Then, the three values (ACK/NACK/DTX) determination is made based on aDTX threshold Th_(DTX) _(—) _(ACK+CQI) and a determination as follows,

if (SIR_(ACK+CQI)<Th_(DTX) _(—) _(ACK+CQI)) (S202 in FIG. 10) “DTX hasbeen transmitted” (S206 in FIG. 10), else “ACK or NACK has beentransmitted” (S204 in FIG. 10),where the determination of ACK/NACK is made from signs of a signalsequence of the HARQ-ACK for a downlink (acknowledgement information ofa downlink shared channel).

In addition to the above-mentioned transmission together with themultiplexed CQI, the HARQ-ACK for DL-SCH (acknowledgement information toa downlink shared channel) may be transmitted in such a manner that itis multiplexed with the CQI and scheduling request or in such a mannerthat it is multiplexed with the CQI and release request. In any of themanners, the DTX threshold Th_(DTX) _(—) _(ACK+CQI+SR) and TH_(DTX) _(—)_(ACK+CQI+RR) may be used for the determination.

If it is determined that the DTX has been transmitted, the base stationapparatus retransmits a downlink shared channel (S208 in FIG. 10). Forexample, the base station apparatus may determine that the mobilestation 100 _(n) fails to receive not a shared channel but downlinkscheduling information in the accompanying PDCCH. In this case, the basestation apparatus may determine the previous transmission to be invalidand retransmit information mapped into a downlink shared channel. Inother words, if the previous transmission is the first one, the currenttransmission is processed as the first transmission. If the previoustransmission is the second one, the current transmission may be alsohandled as the second one.

The above-mentioned HARQ ACK reception method in the case where the ACKis multiplexed with the CQI may be applied to the case where the ACK andthe CQI are encoded together (Joint Coding applied case) or to the casewhere the ACK and the CQI are separately encoded (Separate Codingapplied case).

Alternatively, the base station apparatus may be configured not toperform the above-mentioned ACK/NACK/DTX determination (three valuesdetermination) in the case where the ACK is multiplexed with the CQI.For example, a signal for the above-mentioned acknowledgementinformation may be embedded in a demodulation reference signal in aPUCCH to transmit the CQI as a method of multiplexing theacknowledgement information with the CQI. In this case, it appears tothe base station apparatus that the acknowledgement information isalways transmitted independently of whether the mobile station actuallytransmits the acknowledgement information. Thus, the base stationapparatus would not perform the above-mentioned ACK/NACK/DTXdetermination (three values determination) in the case where the ACK ismultiplexed with the CQI.

(3) CQI Reliability Determination Method

The CQI reliability determination method is performed in accordance withthree steps as presented below.

The CQI reliability determination is made under the case where the CQIis mapped into a PUCCH frequency-multiplexed with a PUSCH as illustratedin FIG. 2.

Step 1:

Obtain a received bit sequence z[n] (n is a bit index) for the CQI. Itis assumed that the number of bits for the CQI transmitted in onesubframe is equal to N. The number N depends on the presence of otherinformation elements (acknowledgement information, scheduling requestand release request) multiplexed with the CQI (S302 in FIG. 11).

Step 2:

Obtain 32 different correlation values in accordance with a formula aspresented below (S304 in FIG. 11), where it is assumed that the numberof information bits for the CQI transmitted in one subframe is equal to5.

The number of information bits for the CQI may be any other value. Forexample, the number of information bits for the CQI may be equal tofour.

${z_{corr}(i)} = {\frac{1}{N} \cdot {\sum\limits_{n = 1}^{N}{{z\lbrack n\rbrack} \cdot {S\lbrack n\rbrack}}}}$

, where s[n] represents CQI code word bits, and i represents a CQIindex.

Step 3:

Perform power determination based on the SIR_(CQI) for the maximumz_(corr)(i) (referred to as MAX[z_(corr)(i)] hereinafter) and a formulaas presented below (S306 in FIG. 11),

if (SIR_(CQI)<Th_(CQI)) “No_Code_Word_Detected” (S308 in FIG. 11)

else “Code_Word_Detected” (S312 in FIG. 11),

where it is assumed thatSIR_(CQI)={MAX[z_(corr)(i)]}²/Interference_(CQI). The parameterInterference_(CQI), is the same as Interference_(CQI) under theabove-mentioned case (2-2) where the ACK is multiplexed with the CQI,scheduling request and release request.

If it is determined that “No_Code_Word_Detected” holds, it is determinedthat the reliability of the CQI is extremely low, and the less reliableCQI is not used in the scheduling and AMC operations (S310 in FIG. 11).On the other hand, if it is determined that “Code_Word_Detected” holds,it is determined the CQI is highly reliable, and the reliable CQI isused in the scheduling and AMC operations (S314 in FIG. 11).

In the above-mentioned embodiment, the SIR for the received bit sequencefor the CQI in the PUCCH into which the CQI is mapped is used, but theSIR for a data demodulation reference signal in the PUCCH into which theCQI is mapped may be used.

[Procedure for Acknowledgement Information Reception Method for DownlinkShared Channels]

An exemplary reception method of acknowledgement information to downlinkshared channels at a base station apparatus is described with referenceto FIGS. 12 and 13. The acknowledgement information to downlink sharedchannels is transmitted in uplinks.

It is assumed below that if the acknowledgement information to downlinkshared channels and CQI are mapped into a PUCCH at both ends of a systemband, resources are divided into resources into which only theacknowledgement information to downlink shared channels is mapped(referred to as resource A hereinafter) and resources where the CQI orthe CQI and the acknowledgement information to downlink shared channelsare multiplexed (referred to as resource B hereinafter). In other words,if a mobile station does not transmit uplink shared channels, the mobilestation uses resources A to transmit only the acknowledgementinformation to downlink shared channels and uses resources B to transmitthe CQI or the multiplexed CQI and acknowledgement information todownlink shared channels. In the transmissions of the CQI, if schedulingrequest or release request are multiplexed and transmitted in additionto the ACK, resources B are used.

In exemplary resource assignment illustrated in FIG. 13, if a subframeis assumed to be for a mobile station to transmit the acknowledgementinformation, resource #2 in resources A is defined as a resourceassigned to the mobile station for the acknowledgement information. Forexample, the resource may have one-to-one correspondence to a resourcenumber for a downlink shared channel corresponding to theacknowledgement information or a resource number for a downlink controlchannel (DL scheduling information) corresponding to the acknowledgementinformation. Resource #n+3 in resources B is defined as a resourceassigned to the mobile station for the CQI if a relevant subframe isassumed to be for the mobile station to transmit the CQI. The resourcenumbers n and m are any natural numbers.

The resources may be frequency resources, code resources or acombination of the frequency resources and the code resources.Alternatively, the resources may be multiplexed in accordance with blockspreading, temporal resources or a combination of the frequencyresources and the code resources. In other words, the resources aredefined depending on multiplexing methods for multiplexing theacknowledgement information to downlink shared channels and the CQI inPUCCHs. If the multiplexing method relates to CDMA, the resourcesconsist of code resources. If the multiplexing method relates to FDMA,the resources consist of frequency resources. If the multiplexing methodrelates to a combination of CDMA and FDMA, the resources consist of acombination of the code resources and the frequency resources. Also,Walsh code multiplexing, CAZAC sequence code multiplexing and/or othersmay be applied in the CDMA.

The acknowledgement information to downlink shared channels may betime-multiplexed with uplink shared channels or mapped into PUCCHs atboth ends of a system band. Furthermore, in the case where theacknowledgement information to downlink shared channels is mapped intoPUCCHs at both ends of the system band, the acknowledgement informationmay be multiplexed with the CQI (the above-mentioned case (2-2)) or maynot be multiplexed with the CQI (the above-mentioned case (2-1). Anexemplary procedure at a base station apparatus of determining thesecases and receiving the acknowledgement information is described below.

At step S401, the base station apparatus determines whether an uplinkshared channel is to be received in a relevant subframe. Specifically,the base station apparatus determines to receive the uplink sharedchannel if the base station apparatus has transmitted scheduling grantto a mobile station and does not determine to receive the uplink sharedchannel otherwise. More specifically, in FIG. 5, subframe #i+3corresponds to a subframe where the uplink shared channel is to bereceived, and subframes other than subframe #i+3 correspond to subframeswhere the uplink shared channel is not to be received. In anotherexample, in FIG. 6, subframes #i+3 and #i+9 correspond to subframeswhere the uplink shared channel is to be received, and subframes otherthan subframes #i+3 and #i+9 correspond to subframes where the uplinkshared channel is not to be received. Even in the case where the ULscheduling grant has not been transmitted to the mobile station, asillustrated in subframe #i+9 in FIG. 9, if NACK has been transmitted asthe acknowledgement information to uplink shared channels, a subframe atthe corresponding retransmission timing would be a subframe where theuplink shared channel is to be received. In other words, if the uplinkscheduling grant was transmitted in a subframe preceding a relevantsubframe by a predefined number of subframes over a PDCCH or if NACK wastransmitted as the acknowledgement information to uplink shared channelsin a subframe preceding the relevant subframe by a predefined number ofsubframes over a PDCCH, the relevant subframe would be a subframe wherethe uplink shared channel is to be received.

If the uplink shared channel is to be received at the relevant subframe(S401: YES), at step S403, the base station apparatus determines whetherthe mobile station 100 _(n) has actually transmitted the uplink sharedchannel. If the base station apparatus determines that the mobilestation 100 _(n) has actually transmitted the uplink shared channel(S403: YES), at step S405, the base station apparatus decodes the uplinkshared channel. At step S407, the base station apparatus determineswhether to receive acknowledgement information to downlink sharedchannels in the relevant subframe. If the base station apparatus is toreceive the acknowledgement information (S407: YES), at step S409, thebase station apparatus receives the acknowledgement informationtime-multiplexed with the uplink shared channel. If the base stationapparatus is not to receive the acknowledgement information (S407: NO),the base station apparatus does not receive the acknowledgementinformation.

On the other hand, if the base station apparatus is not to receive theuplink shared channel in the relevant subframe (S401: NO) or if the basestation apparatus does not determine that the mobile station 100 _(n)has actually transmitted the uplink shared channel (S403: NO), the basestation apparatus checks the PUCCH mapped into both ends of the systemband. To this end, at step S411, the base station apparatus determineswhether to receive the acknowledgement information to downlink sharedchannel in the relevant subframe. More specifically, in FIG. 7, subframe#i+3 corresponds to a subframe where the acknowledgement information todownlink shared channels is to be received, and subframes other thansubframe #i+3 correspond to subframes where the acknowledgementinformation to downlink shared channels is not to be received. In otherwords, if the downlink scheduling information was transmitted in asubframe preceding the relevant subframe by a predefined number ofsubframes over a PDCCH, the relevant subframe would be a subframe wherethe acknowledgement information to downlink shared channels is to bereceived.

If the base station apparatus is not to receive the acknowledgementinformation (S411: NO), the base station apparatus does not receive theacknowledgement information. On the other hand, if the base stationapparatus is to receive the acknowledgement information (S411: YES), atstep S413, the base station apparatus determines whether to receive theCQI in the relevant subframe. If the base station apparatus is toreceive the CQI (S413: YES), at step S415, the base station apparatusreceives the acknowledgement information multiplexed with the CQI mappedinto resources B (resource #n+3) in accordance with the above-mentionedcase (2-2) where ACK is multiplexed with the CQI, scheduling request orrelease request. On the other hand, if the base station apparatus is notreceive the CQI (S413: NO), at step S417, the base station apparatusreceives the acknowledgement information mapped into resources A(resource #2) in accordance with the above-mentioned case (2-1) whereonly ACK is transmitted.

[Procedure for Uplink CQI Reception Method]

An exemplary method for receiving uplink CQI at a base station apparatusis described with reference to FIG. 14.

A CQI may be time-multiplexed with uplink shared channels or mapped intoa PUCCH at both ends of a system band. Furthermore, in the case wherethe CQI is mapped into the PUCCH at both ends of the system band, theCQI may be multiplexed with acknowledgement information or may not bemultiplexed with the acknowledgement information. The base stationapparatus may determine these cases and receive the CQI as follows.

At step S501, the base station apparatus determines whether to receivean uplink shared channel in a relevant subframe. Specifically, if thebase station apparatus transmits scheduling grant to a mobile station,the base station apparatus determines that it is to receive the uplinkshared channel. On the other hand, if the base station apparatus has nottransmitted the scheduling grant to the mobile station, the base stationapparatus determines that it is not to receive the uplink sharedchannel. More specifically, in FIG. 5, subframe #i+3 corresponds to asubframe where the uplink shared channel is to be received, andsubframes other than subframe #i+3 correspond to subframes where theuplink shared channel is not to be received. Alternatively, in FIG. 6,subframes #i+3 and #i+9 correspond to subframes where the uplink sharedchannel is to be received, and subframes other than subframes #i+3 and#i+9 correspond to subframes where the uplink shared channel is not tobe received. Even in the case where UL scheduling grant has not beentransmitted to the mobile station, as illustrated in subframe #i+9 inFIG. 9, if NACK has been transmitted as acknowledgement information tothe uplink shared channel, a subframe corresponding to itsretransmission timing would be to be received in the uplink sharedchannel. In other words, if the uplink scheduling grant was transmittedin a subframe preceding the relevant subframe by a predefined number ofsubframes or if NACK was transmitted as the acknowledgement informationto the uplink shared channel in a subframe preceding the relevantsubframe by a predefined number of subframes over a PDCCH, the relevantsubframe would be to be received in the uplink shared channel.

If the base station apparatus is to receive the uplink shared channel inthe relevant subframe (S501: YES), at step S503, the base stationapparatus determines whether the mobile station 100 _(n) has actuallytransmitted the uplink shared channel in accordance with FIG. 9. If thebase station apparatus determines that the mobile station 100 _(n) hasactually transmitted the uplink shared channel (S503: YES), at stepS505, the base station apparatus decodes the uplink shared channel.Then, at step S507, the base station apparatus determines whether toreceive a CQI in the relevant subframe. If the base station apparatus isto receive the CQI (S507: YES), at step S509, the base station apparatusreceives the CQI time-multiplexed with the uplink shared channel. Inother embodiments, at step S509, the base station apparatus maydetermine the reliability of the CQI in accordance with FIG. 11. If thebase station apparatus is not to receive the CQI (S507: NO), the basestation apparatus does not receive the CQI.

On the other hand, if the base station apparatus is not to receive theuplink shared channel in the relevant subframe (S501: NO) or if the basestation apparatus does not determine that the mobile station 100 _(n)has actually transmitted the uplink shared channel (S503: NO), the basestation apparatus checks a PUCCH mapped into both ends of a system band.To this end, at step S511, the base station apparatus determines whetherto receive a CQI in the relevant subframe. If the base station apparatusis not to receive the CQI (S511: NO), the base station apparatus doesnot receive the CQI. On the other hand, if the base station apparatus isto receive the CQI (S511: YES), at step S513, the base station apparatusdetermines whether to receive acknowledgement information to a downlinkshared channel in the relevant subframe. More specifically, in FIG. 7,subframe #i+3 corresponds to a subframe where the acknowledgementinformation to the downlink shared channel is to be received, andsubframes other than subframe #i+3 correspond to subframes where theacknowledgement information to the downlink shared channel is not to bereceived. In other words, if downlink scheduling information wastransmitted in a subframe preceding the relevant subframe by apredefined number of subframes over a PDCCH, the relevant subframe wouldbe a subframe for receiving the acknowledgement information to thedownlink shared channel.

If the base station apparatus is not to receive the acknowledgementinformation (S513: NO), at step S519, the base station apparatusreceives the CQI mapped into resources B (resource #n+3) in the PUCCH.On the other hand, if the base station apparatus is to receive theacknowledgement information (S513: YES), at step S515, the base stationapparatus determines whether a mobile station has actually transmittedthe acknowledgement information in resources B (resource #n+3) inaccordance with the above-mentioned case (2-2) where the ACK ismultiplexed with the CQI, scheduling request or release request. If thebase station apparatus determines that the mobile station has actuallytransmitted the acknowledgement information (S515: YES), at step S517,the base station apparatus receives the CQI multiplexed with theacknowledgement information in resources B (resource #n+3) in the PUCCH.If the base station apparatus determines that the mobile station has nottransmitted the acknowledgement information (S515: NO), at step S519,the base station apparatus receives the CQI mapped into resources B(resource #n+3) in the PUCCH.

In this embodiment, at step S515, the base station apparatus determinesthat the mobile station has actually transmitted the acknowledgementinformation in resources B (resource #n+3). In other embodiments, atstep S515, the base station apparatus may always determine that themobile station has actually transmitted the acknowledgement information.For example, a signal for the acknowledgement information may beembedded in a demodulation reference signal in the PUCCH fortransmitting the CQI in order to multiplex the acknowledgementinformation with the CQI. In this case, it appears to the base stationapparatus that the acknowledgement information is always transmittedindependently of whether the mobile station has actually transmitted theacknowledgement information. Thus, at step S515, the base stationapparatus would always determine that the mobile station has actuallytransmitted the acknowledgement information.

In this manner, according to the embodiments of the present invention,the base station apparatus can be achieved for appropriate schedulingand HARQ operations in uplinks and downlinks in LTE.

In the above-mentioned embodiments, it has been assumed that RRT (RoundTrip Time) for HARQ in uplinks and downlinks is equal to 6, but thepresent invention is not limited to the RRT value. For example,apparatuses and operations according to embodiments of the presentinvention may be applied to RTT equal to 8 in uplink and downlink HARQ.

Although the present invention has been described by way of the abovespecific embodiments, the present invention is not limited to them.Various alternative embodiments, implementations and operations will beconceived by those skilled in the art from this disclosure.

In other words, it is understood that the present invention encompassesother embodiments not disclosed herein. Thus, the scope of the presentinvention can only be defined via accompanying claims.

For convenience, the present invention has been described with referenceto the distinct embodiments, but separation of the embodiments is notessential to the present invention and two or more of the embodimentsmay be used together as needed. Some specific numerals have been used tofacilitate understanding of the present invention, but unless otherwisenoted, these numerals are simply illustrative and any other appropriatevalues may be used.

The present invention has been described with reference to the specificembodiments of the present invention, but the embodiments are simplyillustrative and variations, modifications, alterations andsubstitutions could be contrived by those skilled in the art. Forconvenience of explanation, apparatuses according to the embodiments ofthe present invention have been described with reference to functionalblock diagrams, but these apparatuses may be implemented in hardware,software or combinations thereof. The present invention is not limitedto the above embodiments, and variations, modifications, alterations andsubstitutions can be made by those skilled in the art without deviatingfrom the spirit of the present invention.

This international patent application is based on Japanese PriorityApplications No. 2007-052112 filed on Mar. 1, 2007 and No. 2007-121301filed on May 1, 2007, the entire contents of which are herebyincorporated by reference.

1. A base station apparatus for communicating to a mobile station over adownlink shared channel, comprising: a reception unit configured toreceive downlink radio quality information from the mobile station overa control channel frequency-multiplexed with an uplink shared channel; ameasurement unit configured to measure a radio quality of the controlchannel; and a determination unit configured to determine reliability ofthe downlink radio quality information based on the radio quality. 2.The base station apparatus as claimed in claim 1, wherein the radioquality includes at least one of a ratio between a receive power levelfor a data demodulation reference signal in the control channel and aninterference power level and a ratio between a receive power level for acontrol signal in the control channel and an interference power level.3. The base station apparatus as claimed in claim 1, wherein thedetermination unit is configured to determine that the reliability ofthe downlink radio quality information is insufficient or that themobile station has not transmitted the downlink radio qualityinformation if the radio quality is lower than or equal to a predefinedthreshold.
 4. The base station apparatus as claimed in claim 3, furthercomprising: an out-of-synchronization determination unit configured todetermine that an uplink for the mobile station is out ofsynchronization if it is determined that the mobile station has nottransmitted the downlink radio quality information.
 5. The base stationapparatus as claimed in claim 3, further comprising: a discarding unitconfigured to discard the downlink radio quality information if it isdetermined that the reliability of the downlink radio qualityinformation is insufficient.
 6. A communication control method at a basestation apparatus for communicating to a mobile station over a downlinkshared channel, the method comprising: receiving downlink radio qualityinformation from the mobile station over a control channelfrequency-multiplexed with an uplink shared channel; measuring a radioquality of the control channel; and determining based on the radioquality whether the mobile station has transmitted the downlink radioquality information.